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LOS ANGELES — Some hybrid car owners in California are fast approaching the day when they will be allowed to drive solo in car pool lanes.

State lawmakers passed a bill last year that gave some types of the high-mileage, low-emission vehicles access to the coveted lanes — a privilege meant to encourage drivers to buy the environmentally friendly cars.

California’s law was supposed to take effect Jan. 1 but first needed approval from the federal government. That permission was tucked into a $286 billion transportation bill Congress passed last week, meaning there is just one last strand of red tape keeping hybrids out of the high-occupancy vehicle lanes: State air regulators need to clarify which vehicles meet the mileage and emissions standards.

The policy’s supporters hope hybrids will be allowed in the car pool lanes by year’s end.

“Knowing that you’re able to drive in that car pool lane would be huge, and I think it would attract others to say, ‘Hey, I should have a car like this as well,”’ said Andrew Werts, a 31-year-old marketing director from Redondo Beach who recently sold his SUV and bought a Toyota Prius.

Not all eligible
Only two other models — Honda’s hybrid Civic and Insight — meet the eligibility standards of at least 45 miles per gallon and almost no smog-causing emissions, according to an aide to the author of California’s bill, Assemblywoman Fran Pavley, a Democrat.

California Air Resources Board attorneys are reviewing the bills to determine officially what vehicles will qualify, said spokeswoman Gennet Paauwe.

Hybrids get better mileage by supplementing gas with electricity harnessed from the engine during braking and coasting, but some are more efficient than others.

California will become the second state to allow hybrids with just one person in the car to use car pool lanes. Virginia enacted the change in 2000, and Arizona, Connecticut, Georgia and Minnesota are considering it.

In Virginia, some drivers complain that opening the door to hybrids has led to a crush of cars and slowed once-speedy commutes.

Activist concern
The American Lung Association of California advocates hybrids but took no stand on the car pool bill for fear it might cut car pooling and lead to more pollution.

“We were not convinced that this incentive was needed and we were concerned about the potential to slow traffic in HOV lanes and discourage people from car pooling,” spokeswoman Bonnie Holmes-Gen said.

To prevent hybrids from clogging car pool lanes, Pavley’s bill expires in 2007 and caps at 75,000 the number of hybrid vehicles that could participate. Owners would have to pay about $8 for decals identifying their vehicles as hybrids to police.

As of the end of June, there were 57,164 hybrids registered in California, though not all would be car pool-eligible, according to the Department of Motor Vehicles.

In a sign of the vehicles’ growing popularity, nearly 24,000 hybrids were registered in the first six months of this year.